The present invention relates to a pressure control unit for the control of at least one gas depending on the pressure of another gas comprising a reference pressure chamber, in which the pressure is adjustable, and at least one control chamber, through which the gas to be controlled is lead, control chamber being separated from the reference chamber by means of a membrane system, which is connected to a spring-loaded control valve in the gas inlet to the control chamber.
A pressure control unit of this kind is known in which one gas is supplied to the reference pressure chamber via a usual pressure regulator and the pressure in the reference pressure chamber causes a corresponding control of the pressure of the other gas which is supplied to the control chamber. By changing the pressure in the reference chamber an equal change of the pressure of the other gas is provided as a constant pressure difference is maintained between the two gases determined mainly by the elastic forces of the membrane system and the spring-load of the control valve.
This control with a constant pressure difference results in a varying ratio of the pressures when these are changed, which, however, is adverse to most applications and it has therefore often been attempted to overcome this drawback by different measures.
The object of the present invention is to provide a proportional pressure control of one or more gases depending on the pressure of another gas, i.e. a simultaneous control of the pressures, so that the ratio of them remains essentially constant when they are changed.